Electrical heating unit



Feb. 24. 1925.

L. D. SMITH ELECTRICAL asume uuu- 2 Sheets-Sheet 2 py a atto: www' Patented Feb. 24, 1925.

LUTHER D. SMITH,

PATENT oF-Fice.

or Tomo, omo.

Emcmcn. mme UNIT.

Application mea February s, 1924. serial no. 091,353.

To all twhom t may con/:em: A

Be it known that I, LUTHER D. SMITH, a citizen of the United States, and a resident of Toledo, in the county of Lucas and State of Ohio, have invented a new and useful Electrical Heating Unit, which invention is fnlly set forth in the following specification.

f. This invention relates-.to electricalheating units of the type commonly used in 1 electric cook stoves, hot plates and the like. In heating units' of this class, the partwhich is most liable to and frequentlyA breaks, thereby requiring replacement, is

the heating or resistance ,coil or element. With all of the heating units now used,'s`o far as I am aware, it is a diiicult and expensive matter to replace a Worn out or broken resistance coi or wire, such work usually requiring the services of electrician or one skilled in making such repairs, thereby involving considerable delay, expense and annoyance. With many of the electric stoves or hoty plates now used, it is necessar7 to replace the entire electrical unit if the resistance wire or other part of the unit becomes broken.

The primary ob'ect of the invention is the provision of a described, the resistance. element of which when broken is capable of -being easily and quickly replaced by a maid or housewife without disturbing the position of the unit in the stove or hot platein which it is located, thereby saving the time, expense and trouble incident to calling in anelectrician or/mechanic to make the change. Another object of -the invention is the provision of a refractory plate or resistance element carrying member of novel and improved construction, whereby it is more efficient in its function and is capable of be"-I ing assembled' with the other parts of a unit in an easier and more effective manner. Anothery object of the invention is the manner emplo ed for maintaining the coil or resistance e ement in the refractory plate of the unit. and -bf connecting it -with a source of electrical supply and controlling it, whereby successive parts or sections of theV coil or element may be' practically eating unit of theclass placed in closedpcircuit enabling all or Il,V greater or less portion 4olLthe element to be used as the heating desired may require.

Other lobjects and advantages of the in-l u vention will be apparent from the followl ing detailed description thereof. v

While the invention in its broader` aspect is capable of embodiment 'in numerous forms, a preferred embodiment thereof is oo illustrated in the accompanying-drawings, in whicl1,

Figure 1 is a fragmentary perspective view of a stove top ,with al unit embodying the `invention mounted -therein and'in Sec- 65 tion, as along a 1ine-13 in Fi Fig'. 2 is a top plan view of a unit em dying the invention with the pan member. thereof partly broken away and comprisin la cast ing, and with a circuit control s own` in connection therewith. Fig. 3 is a section on the line .3 3 in Fig. 2, and Fig. 4 is a. section on theI line 4 4 in Fig. 2. Y

Referring to the drawings, 1`designates the top of a stove or hot p ate having one 76 or more openings 2 therein for receiving an electrical heatin unit. The portion ofthe stove immediate y surrounding the opening 2 is preferably, though not necessarily, raised as `at 3, and the free' of the raised'go portion is turned downwar to form a 'iiange 4. A pan 5, which may b of sheetmetal, as shown in Fig. 1, or cast, as sho'wn in Figs. 2, 3, and 4, or made in any other manner, as-desined, is preferably slightl g5 `larger in diameter than' the hole 2 Wit whichy it is associated, and the'upperfree edge of the pan is provided with an outwardly turned flanve 6 for seating up against the under side of the raised 'portion- 90y 3 of the top, preferably in outwardly spaced relation to the' top ange 4. The pan ange 6 is secured to the to 1 by electric welding, riveting or' lin any ot er suitable manner.

The refractory element or plate lofthe 9,5 unit is designated 7 and is cu'stomaril. of percelain. This element is circular in orm and of a. size to lit into the associated opening 2 and down into the pan 5 with its side wall preferably sli htly spaced from the '10o maginal tlange 4 o the g to allow -for contraction and expansion of the parts under changing heat conditions. It is desirable to heat-insulate the refractory plate 7 from the pa.n.5, and for such purpose the plate is spaced from the bottom of the pan and in some instances from its side walls to permit a heat-insulating packing 8 of asbestos, mineral Wool or other suitable material to be packed therein.

An important feature of the invention consists'in providing the bottom of the refractory plate 7 with a plurality of integral legs 9, in the present instance three 1n number, which rest on the bottom of the pan 5 and maintain the plate in permanent spaced relation thereto, thus facilitating mounting the plate in the pan, and requiring less slnll and time in assembling the plate and pan and in packing the heat-insulating material 8 therebetween in such quantity that the. plate will bear the desired relation to the pan and to the stove top. A hole 1G is provided longitudinally through cach leg 9 and plate body to receive a retaining bolt 1l, which extends therethrough and through a registering opening in the pan bottom and,

ym the presentinstance, has its head shouldering in an enlarged top portion` of the opening and has its nut acting against the underside of the pan bottom, as shown 1n Figs. 1 and 4. The screw member of the bolt has its head grooved to' enable a screw driver to be used over the top ot the unit to disconnect the plate and pan.

The refractory plate 7 is formed on its top ywith a resistance element receiving 'groove 12 which, in the present instance,.

is of convolute form and extends out from the center of the plate in progressively enlarging convolutions to near 'the outer edge of the plate. The resistance element employed inthe present instance comprises a wire coil 13, which seats in and follows the convolutions of the groove 12 and, in the present insta-nce, is separated into three sections a, b and c connected in 'series and adapted to be progressively1 placed in closed circuit thereb 1 enabling the heating action i 5 of the unit to b e regulated as desired. The inner section a is connected at its inner end to a. central binding post 1-1' and at its outer end to an intermediate binding post 15. The section 7) is connected at 'its inner end to the binding ost 15 and at its outer end to an intermedlate binding post 16. and the section c is connected at i-ts inner end to the 'binding post 16 and at its outerend to an outer binding post 17. The several binding posts 14, 15, 16 and 17 are connected through a. suitable control 18 with a source of electrical current supply, so that the sections ofthe heating element 13 may be progressively placed in closed circuit with the l source of .supply either outwardly from the inner section a or inwardly from the outer the full number, or all' of the sections, to Y be rendered operative as Vconditions may require'. The manner of connecting the different ,sections ot' the heating element, so that some or all may be placed in .closed circuit, is well understoodin the art and need not, therefore, be specifically described or shown. p

.lf a groove or channel 12 of the open top type is employed for receiving the heatingelement 13, it is preferable to provide one or both walls ot' the groove at intervals with overhanging projections 19 to retain the coil or element 13 within the groove. lf the space left between the outer ends of the projections 19 and the opposed wall of the groove is less than the diameter of the coil 13. as illustrated in the present case, it will be necessary in placing acoil in the groove to thread it through the same under the projections.

The connections of the several binding posts 14,- 15, 16 and 17 with the respective circuit wires 20 are disposed below the pan 5. In order to' enable the heating element 13 of the sections thereof, if it is of sectional form, vlo be easily connected o r disconnected from the respective binding posts at the top of the unit and without necessitating a removal of the unit from the stove the binding posts are Amade of sectional form each comprising an anchoring sleeve 21, a lower threaded stem 22V to which the respective circuit wire 20 is connected and a top screw which binds the adjacent end of the coil 13 or of'a section thereotto the sleeve 21. Each binding post is mounted in a tubular bottom extension 24 of the refractory plate 7 each of such extensions extending through a registering opening in the bottom ofthe pan 5 and preferably a l short distance below the saine and having its bore extending up through the body of the plate. The anchoring sleeve 2l is mounted in tbe upper port-ion of said bore and is preferably provided with a head which is square or of other form than round.

moving an associated screw 23 'from the sleeve, and a new element may be as easily connected therewith. This isaveryim-y portant feature in heating units ofthe class described as it enables broken'heating elements to be replaced -in an exceedingly simple and easy manner ,without necessitating the/calling of an electrician. or mechanic' for such purpose, and it also obviates the necessity of replacing the entire' imit, as is now so often the case when a heating element has become broken. I

I wish i-t understood that my invention is not limited to any specific construction, ar-

rangement or form of the parts, as it' is capable of numerous modlications and changes without, departing from the 'spirit of the claims. 4 Y y I-Iaving thus described my invention, what I elaimas new and desire to secure by Letters Patent is;

l. In combination with a plate havingoan` opening with the marginal part thereof raised and the Ifree edge flanged downwardly to forma circular channel, al pan having Ia perforated bottom and a rim `the free edge Iof which is flanged outwardly and secured iii the channel, a grooved refractory element in the pan engaged at its periphery with the flange of the plate and having a series of spaced dependin legs seated on the pan bottom, heat insu ating material be-v tween the periphery of the element and the pan rim and between the pan bottom and the under face of sa'id element, hollow depend ing members' carried by the element and eX- tending through said perforations'- of the pan bottom, means extending through the legs and engaging the pan bottom to secure the element to the pan, resistance means in the groove rof the element and means engaged in the tops of the hollow members orY the element to removably secure the resist-l ance means in position.

2. In .combination with a plate having an opening, a pan havingv a perforated opening disposed vbeneath and in register with the opening and secured to the plate, a ooved1 refractory element in the pan having de'- pending legs seated on the pan bottom to hold the bottom of the element spaced above the pan bottom, heat insulating material in said space between the pan bottom and element, means extending through the legs and pan bottom to secure the element to the pan, resistance means removably mounted in the groove of the element,`hollow depending extensions on the element extending through the perforations of the lvpan bottom, a con-` ductor in each extension,l means connected\\ to one endo` each conductor and operable from the top of the element to removably secure the resistance means in position, and current. conveying means removably connected tothe conductors and disposed below the element.

3. In an electric heating unit,J a refracopening. and a pan registering tory element grooved onA its upperfaceand formed with a series of depending parts, a pan having perforations in its bottom, some of said parts seating on Athe pan bottom and other Iof the parts extending through thev perforations in the pan bottom, means to se- .cure the first named of the said parts to the pan bottom, resistance means in the groove of the element, means carried by the other of Said parts and operable from the' top of the element to removably secure the resistance means in the grooves, and means con-- pending hollow parts in register with the groovevvmetal sleeves in said hollow parts, means operable from 'the top of the body to connect the resistance means to the sleeves, and combined means to supply current to the sleeves and to hold the latter against upward movement.

5. In an electric heating unit, a refractory body grooved on its upper face, resistance meansin-the groove, said 4'body having depending hollow parts in register with the groove, metal sleeves invsaid hollow parts, means Aoperablefrom the top of the 4body to connect the resistance meansY to -the sleeves, and means to supplycurrent to the r resistance means.

6. In combination with a plate having an opening, a pan'of greater diameter than that of, the opening vsecured to and depending from the late and havin a perforated bottom, a re actory groov r body in-the opening having a pluralitylof depending tubular legs. which seat upon the pan bottom and register with the perforations in the pan bottom,l insulation between the pan and body, resistance means in the groove of the body, means extending through the tubular .legs to secure the body to the pan bottom, and means to supply current to the resistance means.

7 In combination with a plate having an opening and secured to the plate therebeneath, a refractory body in the panhaving depending tubular parts and having a grooved upper face in register with the tubular parts, said pan having perforations in i'ts'bottomthrough which said tubular parts'proj ect, resistance means in the groove f of the body, means in the tubularl parts supply current to the resistance means4 and with the means operable romabove the bodyto re r Arnovably connect the resistance meansto the current supplying means. I

.8. In combination with a plate having 'an' opening and a pan registering Iwith* the opening and scurvd i'o the phx'h thorehnluncronds thereof, und Inezmsopcrablc from neath, z1- refrmztm'y bodym the pun having above the body to rvmova'bly connect the redepending;` tubular puits und. having n sistancc means to the curljent supplying 1f" grooved upper face in regidor with tlnl tumeans.

hular parts, rcsistanvc tninnr; in the 5rnm'cI In testimony. whereof' I have hereunto of the body,v curl-ent supplying lncnns oxsnhscl'lhvfl my nume to tinaI specxcatlon. tendmg into the tubular parts through the LUTHER D. SMITH. 

